1. Field of the Invention
The present invention relates to an electronic azimuth meter and, more particularly, to the correction or calibration of the electronic azimuth meter and to an electronic timepiece having the electronic azimuth meter.
2. Description of the Prior Art
There is known an electronic azimuth meter having X-direction and Y-direction magnetic sensors comprising MR (magnetoresistive effect) elements for detecting intensity of a magnetic field with regard to respectives of two directions X and Y orthogonal to each other and calculating azimuth from the X-direction and Y-direction magnetic fields detected by the magnetic sensors. Further, it is also known that according to the electronic azimuth member, since a magnetic field by the geomagnetism is inherently small, when a portion of material constituting the azimuth meter is magnetized, a magnetic field produced by the magnetization is superposed on the magnetic field produced by the geomagnetism, a magnetic field sensed or detected by the magnetic sensors is deviated from the magnetic field produced by the geomagnetism and as a result, the azimuth is difficult to measure accurately.
Further, it is also known that in order to correct influence of remnant magnetization of a material of a constituent member of such an electronic azimuth meter, there are measured maximum values and minimum values of magnetic field detecting values by respectives of X-direction and Y-direction magnetic sensors when azimuth of the electronic azimuth meter is variously changed and the magnetic field detecting values are corrected based on the maximum values and the minimum values (for example, Japanese Patent Publication No. 30364/1987).
However, as described above, since the magnetic field produced by the geomagnetic on the earth (surface thereof) is inherently small (at a vicinity of Tokyo, the horizontal magnetic horizontal force is about 30 xcexcT (strictly speaking, magnetic flux density), further, the dip is about 50 degree, the declination is about 6 degree to the west), detected output of the magnetic field is also small, there is a concern that a variation caused by noise is difficult to avoid and accordingly, accurate determination of the maximum values and the minimum values simply and in a short period of time, is not necessarily facilitated actually.
Further, since the magnetic sensors of the electronic azimuth meter detect magnitudes of components in predetermined directions of the magnetic field (magnetostatic field) or the magnetic flux density in the air, there is no actual benefit in discriminating between the magnetic field and the magnetic density in the air and, therefore, in the specification, the technical term of the magnetic field is used.
The present invention has been carried out in view of the above-described problem and it is an object thereof to provide a correcting mechanism of an electronic azimuth member facilitating to determine the maximum values and the minimum values, an electronic azimuth meter having the correcting mechanism and an electronic time piece having the electronic azimuth meter.
In order to achieve the above-described object, according to the invention, there is provided a correcting mechanism of an electronic azimuth meter having an X-direction magnetic sensor and a Y-direction magnetic sensor for detecting intensities of a magnetic field in two orthogonal directions X and Y and constituted to calculate an azimuth from magnetic field detecting values of the X- and the Y-direction magnetic sensors, comprising storing means for storing respectives of a maximum value and a minimum value with regard to the magnetic field detecting value by each of the X-direction and the Y-direction magnetic sensors, updating means for updating the maximum value or the minimum value to a newly detected magnetic field detecting value when the magnetic field value which is newly detected by each of the X-direction and the Y-direction magnetic sensors is larger than the maximum value stored in the storing means or smaller than the minimum value stored therein, azimuth change inducing means for providing a display of inducing a continuous change of the azimuth of an electronic azimuth meter main body over a range larger than 360 degree, predicting means for predicting that the maximum value or the minimum value in the X- or Y-direction is a true value when each of the maximum values and the minimum values of the magnetic field detecting values in the X-direction and the Y-direction is not updated during a predetermined time period in accordance with rotation of the electronic azimuth meter main body in accordance with an induction display of the azimuth change inducing means and canceling a prediction indicating the true value when the maximum value or the minimum value predicted to be the true value is updated by the updating means, and stop control means for stopping an updating processing by the updating means when all of the maximum values and the minimum values in the X-direction and the Y-direction are predicted to be the true values and induction by induction display of the azimuth change inducing means reaches 360 degree or more.
In the correcting mechanism of an electronic azimuth meter according to the invention, there are provided xe2x80x9cthe updating means for updating the maximum value or the minimum value to the newly detected magnetic field detecting value when the magnetic field detecting value which is newly detected by each of the X-direction and the Y-direction magnetic sensors is larger than the maximum value stored in the storing means or smaller than the minimum value stored therein, and predicting means for predicting that the maximum value or the minimum value in the X- or the Y-direction is the true value when updating is not carried out during a predetermined time period in accordance with rotation of the electronic azimuth meter main body in accordance with the induction display of the azimuth change inducing means with regard to respectives of the maximum values and the minimum values of the magnetic field detecting values in the X-direction and the Y-directionxe2x80x9d, and accordingly, with regard to respectives of the X-direction and the Y-direction, (except that an initial detecting value is adopted as the maximum value or the minimum value) so far as the magnetic field detecting values are provided in the forms of a maximum and a minimum, the magnetic field detecting values are adopted as the maximum value and the minimum value.
Further, according to the correcting mechanism of the invention, xe2x80x9cthe azimuth change inducing means is constituted to provide the display of inducing the continuous change of the azimuth of the electronic azimuth meter main body over the range of at least 360 degreexe2x80x9d, further, xe2x80x9cthe stop control means is constituted to stop the updating processing by the updating means when all of the maximum values and the minimum values in the X-direction and the Y-direction are predicted to be the true values and the induction by the induction display of the azimuth change inducing means reaches 360 degree or morexe2x80x9d and accordingly, with regard to respectives of the X-direction and the Y-direction, the magnetic field detecting values provided as the maximum value and the minimum value are selected from detected values with regard to the azimuth of 360 degree, that is, all of the azimuth and therefore, the magnetic field detecting values can be the maximum value and the minimum value in two directions in principle.
Further, according to the correcting mechanism of the invention, xe2x80x9cthe continuous azimuth change induction display by the azimuth change inducing means is constituted to be able to carry out over a range larger than 360 degreexe2x80x9d and xe2x80x9cthe update stop processing by the stop control means is constituted to carry out so far as all of the maximum values and the minimum values in the X-direction and the Y-direction are predicted to be the true values and the induction display by the azimuth change inducting means reaches 360 degree or morexe2x80x9d and accordingly, even when jitter is caused by superposing noise on a magnetic field detecting output by noise, values proximate to the maximum value and the minimum value are firmly detected and the correction can be carried out.
That is, assuming that when there is started inducing operation for correction at a vicinity of an azimuth at which the magnetic field detecting value by the X-direction or the Y-direction magnetic sensor becomes just a maximum or a minimum, for example, at a location in which the magnetic sensor is rotated just by 360 degree and returns to a starting azimuth, at the location of the azimuth to be stopped, the magnetic field detecting value takes a value of upper or lower peak or proximate to the maximum or the minimum value. However, the magnetic field detecting value is changed in a sine curve with regard to the azimuth and accordingly, at the vicinity of the upper or the lower peak or the maximum or the minimum value, azimuth dependency of the magnetic field detecting value is inconsiderable and therefore, when noise is superposed, there is a concern of updating the maximum value or the minimum value immediately prior to the azimuth intended to stop. Further, the geomagnetism to be detected by the electronic azimuth meter is inherently weak and accordingly, the detecting output of the magnetic field of the geomagnetism is liable to undergo influence of noise and accordingly, there is a concern which is difficult to avoid in updating the maximum value or the minimum value by such a noise, as a result, there is a concern that the correcting operation cannot be finished properly.
In contrast thereto, in the case of the correcting mechanism of the invention, even when the maximum value or the minimum value is updated immediately prior to stop the sensor by being superposed with noise in a direction of increasing the peak at a location at which the sensor is rotated just about 360 degree and returns to the vicinity of the starting azimuth, the azimuth change inducing means induces azimuth change rotation of the electronic azimuth meter main body by exceeding 360 degree and is xe2x80x9cconstituted to carry out the update stop processing by the stop control means only when all of the maximum values and the minimum values in the X-direction and the Y-direction are predicted to be the true valuesxe2x80x9d and accordingly, in the range exceeding 360 degree, until the updated maximum value or the minimum value is predicted to be the true value again, the correcting operation is continued, actually proper maximum value or minimum value is provided and there is hardly a concern of failing correcting operation. Further, the same goes with the case in which noise is superposed in a direction of reducing the peak at start of correcting operation.
In sum, the characteristic of the correcting mechanism of the electronic azimuth meter according to the present invention as described above resides in the correcting mechanism of the electronic azimuth meter having the X-direction magnetic sensor and the Y-direction magnetic sensor for detecting intensities of the magnetic field in the two orthogonal directions X and Y in which the azimuth change inducing means for inducing continuous change of the azimuth of the electronic azimuth meter main body is constituted to provide the induction display over a range larger than 360 degree.
The magnetic sensor may be provided with any constitutions so far as weak magnetic field such as the geomagnetism can be detected and the magnetic field detecting values in the two orthogonal directions X and Y can be provided.
The azimuth change inducing means typically comprises a rotating mark. However, other constitution may be used so far as the azimuth meter main body can be rotated by the user in accordance with induction by the azimuth change means. When the display unit is constituted by liquid crystal display, the mark is typically a conspicuous mark and the mark is, for example, winked. However, the mark may be conspicuous in view of color or shape. When the display unit of a mechanical mechanism, the mark may be, for example, a hand of a time piece.
When the correcting operation has been finished, the stop control means finishes the updating processing by the updating means. Thereby, the maximum detecting value and the minimum detecting value of the magnetic field in the X- and Y-directions stored to the storing means at the time point, are used as reference values of determining the azimuth by the electronic azimuth meter. As described above, when the maximum detecting value and the minimum detecting value in the X- and the Y-directions for constituting the reference values for determining the azimuth, are changed by putting in and out a constituent member of the electronic azimuth meter which is easy to carry remnant magnetization, for example, a button type battery or interchanging the battery to a new one, the maximum detecting value and the minimum detecting value in the X- and Y-directions may be corrected again by carrying out new correcting operation.
Further, when the correcting operation has been finished, the stop control means stops the updating processing by the updating means and so far as the maximum values and the minimum values in the X-direction and the Y-direction stored to the storing means are used in the measurement processing of the azimuth meter, when desired, detection of the magnetic field by the magnetic sensors, reading and detecting the detected magnetic field may be continued.
Further, the stop control means is preferably constituted to stop also the induction by the induction display of the azimuth change inducing means when the updating processing by the updating means is stopped. Thereby, consumption of battery energy can be minimized. However, induction (typically rotation) operation of the induction display of the inducing means may not be stopped and only display by display apparatus comprising the liquid crystal display apparatus may be switched from the azimuth meter correction mode to the correction display mode. Further, the stop control means may preferably be also constituted to make the azimuth change inducing means stop the induction by the induction display when the updating processing is stopped.
The electronic azimuth meter according to the invention is provided with the above-described correcting mechanism and an electronic time piece with an electronic azimuth meter according to the invention is provided with the electronic azimuth meter having the above-described correcting mechanism and is typically constituted to be switchable between the azimuth display mode and the time display mode.